Flexible Electromechanical Punching Device

ABSTRACT

A flexible electromechanical punch device mounted on, or controlled by, a robot arm or similar is disclosed. In one example embodiment, it is further intended to hold a series of punch tools and cushion, or a multiple tool, connected to a multiple punch which, in itself, may be connected to a base body with attached linear gear system and electromechanical drive unit over a tool change system, in such a syncronized way that a spring retract system will be eliminated and that full control of the punch tool position in all directions will be met and that full feedback of motor current and position of the tool during penetration makes it possible to determine that a good punch has been performed relative the supposed material to be punched.

TECHNICAL FIELD

The present invention relates to a flexible punching device which is intended to be included in a robot arm for automatic punching. It may be the last link to a robot arm or similar. It may also be floor mounted, where a robot manipulates the detail to be punched.

BACKGROUND ART

Industrial punching machines are well known and have been in use for many decades. They are especially used in line production for example for the production of car body parts or the like. The machines must in such applications have a certain size, configuration of tools and rigidity so they can contain the whole part, which are to be punched, to receive the right position and tolerances of the holes with correct quality of the cut.

The machines itself is built by basically four individual items. One is the lower table containing a fixture device shaped as a negative of the actual part to be punched. This negative need to contain one cushion for each individual hole to be punched, regardless of the shape of the hole. The second is the upper table containing a series of punch tools with the correct size. The upper table usually need to have a vertical or movement corresponding to the actual distance the punch tools need to have for penetrating the material to be punched. Additional to this, the upper table usually need to have a vertically or rotational travel corresponding to the height of the part to be punched, for one to be able to load and unload the machine.

This is a so called daylight of the machine. A typically value of the daylight of a punching machine for e.g. car bumpers is 2.5 times 1.5 metres. The third is non-parallel hole punchers. The upper table contains individual punch-tools, usually hydraulic driven, for every hole that are not parallel to each other in a three dimensional object which shall be punched. Every one of these tools need to have a devise for spring-back. When punching through material with conventional hardened tools, regardless if it is metal or plastic or others, there will be a friction force generated when the punch tool retracts back through the part. This applies a force into the part that might be dislocated from the lower table if not considered. To overcome this problem, conventional punchers contains a device surrounding the actual tool which is applying force on to the part in the counter-direction of the force implemented by the tool.

The fourth basic part is the frame. The frame need to be big and rigid enough to hold the lower table, the upper table with the travel considered, all punching tools with corresponding hydraulic cylinders as well as the part to be punched. In the example with car-bumpers, it is not unusual that the conventional punching machine size is 3.5×2×3 m and have a total weight of 1.5 metric ton.

In practice, during a typical engineering session of the part to be punched, there are constant changes implemented to the part to be cut itself. This is especially applicable in the car industry, where design and construction of each component of the car is alive and are subject to changes during the entire time to the start of production. To engineer and build a conventional part-unique punching machine takes several months and is very costly in itself. Additional to this there might be changes during the project face which consumes additional time and money. The machines are mechanically rigid, but they are also rigid in an economical and design essence. They are not easy to rebuild. Also during the entire life of a car, there will be many changes of the parts due to mechanical or design reasons, so called face-lifts.

In most cases of such a face-lift, it require a complete new punching machine due to the fact that a rebuilt of an existing machine take so much time (months) so it is not practical feasible to rebuild. The car industry does not allow such an production stop.

Conventional punching machines does not contain any built-in quality control. The quality control is usually done by the operator manually loading and unloading the machine. The operator perform a visual check, as best of his capacity. It is, however, quite impossible for the operator to determine if the holes are in the right position or have the correct size, considering that usual tolerances of position and size of the holes shall be in a fraction of a millimetre. Therefore, a parallel quality control system in most cases is implemented into the production facility. A, so called, dimensional control jig is often constructed and built or a dimensional measuring machine is used to check the components and parts.

This is, however, time consuming why it cannot be controlling every single part through the production. A typical value is one or two per shift. A normal convention punching machine for e.g. bumpers, instrument panels or inner door panels perform about one part per 30 seconds which give around 1000 parts per shift. In worst case, there might be up to 1000 parts that does not meet the requirements and need to be rejected as scrap.

DISCLOSURE OF INVENTION Technical Problem

Even though the above mentioned known machines have been well developed and have functioned well since many years they have, however, the serious limitation of being non-flexible, difficult and expensive to rebuild and mechanical complex to perform maintenance on. It is also necessary to have one machine for each type of product to be punched and also contain on punch-tool for every individual hole to be made in that specific product. This makes the production extremely expensive. After the time when the product is taken out from production (program life time) the machine usually often will be shipped somewhere to only produce spare-parts. Now, the production volume decrease from, maybe, 3000 units per day (3-shift) to 3-4 parts per day. But the machine is equally big still and require a quite big floor area. Bearing in mind, that there are hundreds of parts in a car body that need to be individually punched with different holes for option devices, anyone understand the total requirements of space and cost.

Imagine if it would be possible to produce all different products with all different shapes of holes in just one flexible machine with just a simple change of the actual, low cost, punch tool and also maintain a 100% quality control and a weight of 100 kg or less. What a hit!

Technical Solution

Through the present invention one has been able to meet the above desires and brought about a flexible punching device intended to be a part of a robot arm for punching holes in different locations and with different shapes in different material and which is characterized in that it comprises a base body holding an electrical servo motor or similar, a linear gear construction, a tool-changing device or optionally a rotation or indexing device having pieces around or along containing required tools with correct size and shape, as well as a quality sensor system and having an attachment piece on one end for attaching the complete device to a robot arm or similar and an attachment device automatic attaching a secondary tool construction (multiple punch) holding a rigid arm construction, a punch tool in a bushing and a cushion and a scrap removal system and scrap counter but not a mechanical retract spring system.

According to the invention the base body is mechanically attached to a robot arm or similar.

According to the invention the electrical servo motor or similar is electrically connected with the robot axis computer system as an additional, syncronized, axis.

According to the invention the servo motor or similar is mechanically connected to the base body on one side and to the gear system on the other side.

According to the invention the gear system allows a high speed linear motion and are mechanically connected to the electrical servo motor or similar at one end and indirectly linked to the punch tool at the other end.

According to the invention a tool changing device is mechanically connected to the base body at one end and to the rigid arm in the secondary tool construction at the other end as well as to the punch tool.

According to the invention the rigid arm in the secondary tool construction is mechanically connected to the tool changing device on one end and are connected to the cushion on the other end.

According to the invention the punch tool are mechanically connected to the arm, with free allowance to move in one direction at one side and connected to the tool change system on the other side.

According to the invention, the secondary tool construction can be automatically exchanged to different configurations.

According to the invention, the secondary tool construction can be optionally equipped with rotational or linear device containing different punch tools.

According to the invention the complete system allows a syncronized movement of all axis where the cushion is standing still relative the part to be punched during punching operation and where the punch tool stand still relative the part just being punched during retract allowing a spring retract system to be excluded.

According to the invention, a quality control system is built in, controlling the actual force required to penetrate the material which ensures that the tool is in good condition and will give alarm if the force is too high relative a pre-set value indicating that the tool has been wear or something else has been wrong and indicate that it is time for replacement of the tool preventing that any rejects will be produced. It also, constantly, has a control of the actual position of the punch tool, both relative the part to be punched and relative the punching machine itself. The system will therefore also be constantly aware of that the correct position has been achieved as well as that the punch tool reach the bottom position during every punch ensuring that a hole the whole way through has been done.

DESCRIPTION OF DRAWINGS

The invention will in the following be described more in detail in connection with the attached drawing which describe an embodiment where the punching device shall serve and carry a punch tool and where,

FIG. 1 shows a linear gear system from side

FIG. 2 electromechanichal drive unit

FIG. 3 base body seen from side

FIG. 4 punch tool

FIG. 5 multiple tool

FIG. 6 tool change system

FIG. 7 multiple punch

FIG. 8 assembled punching device

FIG. 9 flexible electromechanical punch device mounted on robot arm

BEST MODE

On FIG. 9 a electromechanical punching device according to the invention is shown which base body is mechanically connected to a robot arm, preferable axis 6 (last axis on a 6 axis robot). The servo motor, as a part in the electromechanical unit, is electrically connected to the robot axis computer and is identified as axis no 7 in a 6-axis robot controller (connected as axis no 5 in a 4-axis robot etc.). The axis no 7, in this case, will be fully syncronized and calibrated to the robot controller meaning that the result will be that the robot actually now is a 7-axis robot. In some applications there will also be possible to control the 7:th axis as a, so called, independent axis. A firm definition of motor characteristics in relation to the mechanical gears will ensure an absolute accuracy of the motor rotational position in relation to the actual value of the punch tool position. The servo motor will be controlled by a drive unit. The axis controller will control and monitor motor current and resolver or encoder values in such a way that the tolerance of the actual position of the punch tool will be less than 0.05 mm. During the punch operation, the 7:th axis may move independent. Full motor current, according to the servo motor specification, is applied to the system for maximum acceleration and speed. The mass inertia together with applied motor torque implement a high mechanical force onto the part to be punched when the punch tool hit the part. The speed and weight of the punch tool system will be opposite proportional to the size of the servo motor for a given punch capacity. A typical dimensional value of motor size is 1/10 of the static force comparing to a hydraulic system. During the penetration of material, the current controller will instantly detect a deviation from a normal characteristic. The system will therefore be able to recognise if the punch tool is damaged or otherwise not suitable to perform a required operation. The system will also be able to detect variations of the material to be punched. Wrong material, wrong thickness or wrong loading position. The wrong loading or robot position is given by the fact that the motor current detection is directly linked to the resolver/encoder value of the axis, and may therefore instantly be able to detect if any force is applied in to the system in any other position than expected.

When the punch tool finally penetrates the material, it will due to the current and resolver/encoder values know that the task was performed correctly. The scrap part will be pushed by the punch tool further down through the cushion. The cushion, however, will be long enough to contain the required number of scrap parts during one operational cycle, e.g. for 10 holes. The friction between the cushion and the scrap part makes the scrap parts to stay in the cushion. The scrap part will just simply travel further down when next hole is punched. After a complete cycle, the robot will move to a container. The punch tool will now travel the whole way through the cushion why the scrap parts will be pushed out and fall down.

After the penetration, there is a relative high friction between the tool and the material just being punched. The system now switch the tool centre point, from earlier top section of the cushion, to the top section of the punch tool. The system will be ordered to move all 7 axis in such a way that the punching tool will retract from the part but not changing the position of the tool centre point relative the part. No forces is applied into the part during this movement When such a movement is done, the part will, in the end of the movement, hit the upper section of the tool holder. At this point, the tool centre point is changed to the top section of the cushion again, and a full retract is performed without the need of a spring retract system.

FIG. 1 shows the linear gear system, a rigid construction converting a rotational movement to a linear movement. The unit is attached with the electromechanical drive unit and the base body.

FIG. 2 shows the electromechanical drive unit, in which a servo motor or similar and, optionally, a planetary gear, or similar, is connected to each other. In many cases, there is no need of a gear onto the servo motor.

FIG. 3 shows the base body which connects to robot flange on one side and the linear gear system and tool change system on the other side.

FIG. 4 shows a punch tool with corresponding cushion

FIG. 5 shows a multiple tool. The multiple tool is the actual part cutting/punching through the material. It is made of conventional material used in normal hydraulic punching machines. There can be, depending on the environment, several tools mounted in the same multiple punch, linear or rotational indexing into the tool holder of the multiple punch device. A typical, reasonable, value is two tool, e.g. shape1 Left and Right.

FIG. 6. shows the tool change system. The tool change system is consisting of mainly two basic parts. The tool changing system is attached on the base body. This unit hold a mechanical device mechanically connecting to the multiple punch through a male or female fit with a cam locking device. The second basic part is a mechanical device connecting to the multiple tool through a radial locking system.

FIG. 7 shows the multiple punch which is the part to be, automatically (or manually) replaced to another multiple tool if a new shape of holes shall be done. This part is configured to fit into the tool change system having corresponding male/female fit. A typical value for the time to change the multiple punch in automatic mode is 4-5 seconds. A set of multiple tools can easily be arranged on a simple table/holder.

The invention is not limited to the embodiment shown, and it can be varied in different ways within the scope of the patent claims. Thus the fastening of e.g. the tool changing device can be located between the body and the gear system and that the equipment can be without tool-changing system totally, all depending of the quantity of different hole shapes to be performed at the time. 

1. Flexible electromechanical punching device intended to be a part of a robot arm or similar for flexible punching of holes with one or several shapes in metal, plastic or any other material, comprising: a base body where a linear gear system, an electromechanical drive unit and a tool change system is attached and automatically or manually is connected to a multiple punch which contain a multiple tool with individual punch tool including corresponding cushion.
 2. Flexible electromechanical punching device according to claim 1; the electromechanical drive unit has a control system syncronized with robot axis controller in such a way that a syncronized movement with all involved axis are performed during retract of the punch tool eliminating the need of an additional spring back retract system.
 3. Flexible electromechanical punching device according to claim 1; wherein the electromechanical drive unit control system momentarily supervise actual current value in such a way that the force will be monitored.
 4. Flexible electromechanical punching device according to claim 1; wherein the electromechanical drive unit control system momentarily supervise resolver/encoder value in such a way that the position of the tool will be monitored.
 5. Flexible electromechanical punching device according to claim 1; wherein a linear gear system is connected to a punch tool, direct or indirect through a tool change device.
 6. Flexible electromechanical punching device according to claim 1; wherein a base body is connected to a multiple punch, direct or indirect through a tool change device.
 7. Flexible electromechanical punching device according to claim 1; wherein the multiple punch may be equipped with a multiple tool arranged in such a way that an indexing, linear or rotational, is performed to place the correct tool into the seat of the multiple tool.
 8. Flexible electromechanical punching device according to claim 1; wherein the waste material in the punching operation will be kept in the cushion until a desired time chosen. 